The present invention relates to a method and/or architecture for accurate time measurement generally and, more particularly, to a method and/or architecture for compensation of crystal start up for accurate time measurement.
Conventional oscillators cannot generate an accurate system clock during a start up condition. In particular, when time keeping accuracy, frequency stability with respect to time and quick start up is required, conventional oscillators are not adequate.
In applications using microcontrollers, if an oscillator has not started up when a power-on-reset (POR) is lifted, the microcontroller can hang. A watchdog timer (WDT) has to be implemented to return the system to a normal mode of operation. Using the watchdog timer will cause significant error (i) if the system is used for time measurement from power up and/or (ii) if an application cannot tolerate the inevitable blackout associated with recovery driven by the watchdog timer.
The present invention concerns an apparatus comprising a first circuit and a timing circuit. The first circuit may be configured to generate an output clock signal that may compensate for oscillation build-up and stabilization time after a power up. The timer circuit may be configured to provide timing in response to the output clock signal.
The objects, features and advantages of the present invention include providing a method and/or architecture for compensation of crystal oscillator start up that may provide (i) high accuracy from point of power application to the chip, (ii) high accuracy over wide voltage and temperature variations, (iii) an accurate timer from power up, and/or (iv) a decreased dead time (e.g., the point beyond which the start up time is not distinguishable).